In general terms, a rolling mill comprises, within a supporting frame, at least two working rolls which bear along a rolling plane on at least two back-up rolls. Tne rolls are carried at their two ends, by means of bearings, in chocks mounted so as to be movable parallel to the rolling plane in apertures made in the sides of the supporting frame. So-called "four-high" mills, comprising two working rolls each bearing on a back-up roll, and so-called "six-high" mills, in which intermediate rolls are interposed between the back-up rolls and the working rolls, are conventionally used. In both cases, the axes of the rolls are arranged in a generally vertical rolling plane, but it is also possible for each working roll to bear on a larger number of intermediate and/or back-up rolls placed symmetrically on either side of the rolling plane.
In order to control the thickness of the rolled product and, in particular, obtain an equal thickness transversely to the rolling direction, the working rolls and, if appropriate, the intermediate rolls are bent or curved by means of bending devices acting on the chocks of the particular roll. A distinction is made between positive bending corresponding to an increase in the distance between the chocks on either side of the plane of the product and negative bending corresponding to a decrease in the distance between the chocks.
In general, for each chock the bending device consists of two sets of jacks arranged symmetrically on either side of the rolling plane and each acting in the desired direction on a bearing part integral with the chock. Normally, each bearing part of the chock bears on two jacks set apart from one another in the axial direction symmetrically on either side of the mid-plane of the bearings of the chock, so that the bending force is effectively distributed over the bearings.
The frame of the rolling mill is symmetrical relative to a mid-plane perpendicular to the rolling plane and corresponding to that of the rolled product. Normally, the rolls are therefore centered on this plane, relative to which the chocks are arranged symmetrically.
However, it may be advantageous to ensure longitudinal movement of these rolls, whether in the opposite direction or not, in order to achieve various aims, such as uniformity of wear of a rolls or the check of the planeness or profile of the rolled product. It will be appreciated that the axial movement of the rolls presents difficulties when these are subjected to a bending force. Consequently, the two operations are usually carried out separately, the bending force being canceled when an axial movement is executed. However, it is expedient, during rolling, to combine the effects of the axial movement and bending of the rolls.
Moreover, the torque is usually exerted on a single pair of rolls, for example the working rolls, and is transmitted to the corresponding back-up rolls by means of friction. But it is necessary for all the rolls to continue to be driven at the same peripheral speed.
Consequently, even if the axial movement is executed when the rolling force is absent, it is useful to maintain a certain amount of bending in order to preserve sufficient friction between the rolls.
So that the axial movement of the rolls can be executed without ceasing to exert bending force, it has been proposed to associate with each movable roll and with its chocks a frame conisisting of two beams which are mounted so as to slide axially on the frame of the rolling mill and on which bear the bending devices which thus move at the same time as the rolls, their chocks and the frame. However, this arrangement renders the production of the rolling mill more complicated and makes it necessary to place four relatively bulky beams inside the mill frame and near the working rolls, i.e., in a space which it is expedient to keep free.